DESCRIPTION: (Applicant's Abstract) Researchers and clinicians in the drug abuse and mental health fields seek to understand the complexities and master the enormous challenges of treating individuals with comorbid drug abuse and psychiatric disorders. Psychiatric comorbidity impacts treatment outcomes in studies with adult substance abuse have been conducted. Studies of adolescent substance abusers consistently reveal high rates of psychiatric comorbidity in community and clinical samples. Researchers have suggested that given the heterogeneity of adolescent substance abuse, important variations in response to treatment may occur based on the type and severity of comorbid psychiatric problems. 183 adolescents with a substance use disorder who participate in a randomized clinical trial comparing family therapy and individual cognitive-behavioral therapy will comprise the study sample. The participants in this study are largely low-income, minority youth with high rates of comorbid disorders. Adolescents and their parents were interviewed at intake to treatment, at the end of treatment, and at 6 and 12 month follow up to determine the level of their substance use and psychiatric symptoms, as well as family problems including parental psychopathology. The purpose of the study proposed in this B/START is to determine whether the presence of psychiatric comorbidity is related to changes in the rate of recovery for adolescents in treatment for drug abuse. The study has three aims: 1) To examine whether specific psychiatric diagnoses are related to changes in adolescent drug use trajectories from intake to the end of treatment and up to 6 month and 12 month follow up; 2) To examine whether severity of psychiatric comorbidity moderates changes in drug use and psychiatric symptom trajectories for adolescent substance abusers; and 3) To examine whether change in parental psychopathology is related to change in adolescent substance abuse and psychiatric comorbidity, and whether treatment modality moderates this relationship. The results of this study will significantly inform the development and refinement of effective interventions for substance abuse adolescents with varying types and severity of comorbid psychiatric problems.